(1) Field of the Invention
The present invention relates to a multi-functional container closure with liner and to a method of producing the same. More specifically, the invention relates to a container closure with liner which can be tightly sealed and which can be easily produced.
(2) Description of the Prior Art
A variety of functions have been imparted to the liner of a container closure by a method (in-shell molding) according to which a thermoplastic resin composition containing such additives as a oxygen absorbing agent, drying agent, deodorant, antibacterial agent, thermo color agent and like agent is molded as a single material in a container closure shell or by a method (packing attachment) according to which a material molded into a sheet is punched into a disc of a size nearly the same as the inner diameter of the container closure and is inserted with pressure in the container closure shell.
Among these additives in the container closure which uses the oxygen absorbing agent, oxygen remaining in the head space of the container must be quickly removed within a period from just after the sealing and keep a low oxygen concentration in the container for storage. In particular, the flavor retentivity of the content is closely related to the concentration of residual oxygen at the time of sterilization or pasteurization treatment. It has therefore been desired to provide a liner blended with an oxygen absorbing agent that is capable of removing oxygen remaining in the container within short periods of time after the sealing.
When the concentrations of additives in the liner are increased such that the additives exhibit their effects to sufficient degrees, the surface hardness of the resin increases and the flexibility decreases resulting in a drastic decrease in the cushioning property and elasticity of the liner material.
Furthermore, development of the functions of the additives due to chemical reactions and physical actions, causes many liner materials to lose their physical properties.
These phenomena directly deteriorate the hermetically sealing property which is most important among the properties required for the liner of the container closure, and it has been desired to solve this problem.